Method of surface-hardening steel, and a quenching medium therefor



United States Patent METHOD OF SURFACE-HARDENING STEEL, AND A QUENCHING MEDIUM THEREFOR Harry L. Mauzy, Houston, Tex., and Edgar L. Von Rosenberg, Oklahoma City, Okla., assignors to Reed Roller Bit Company, Houston, Tex., a corporation of Texas No Drawing. Application February 23, 1956 Serial No. 567,088

6 Claims. (Cl. 148-18) This invention relates to new and useful improvements in methods of surface-hardening steel, and a quenching medium therefor.

An object of this invention is to provide a new and improved method and a quenching medium for treating steel, and particularly high carbon steel, to produce a surface thereon which is uniformly hardened to a high hardness value.

An important object of this invention is to provide a new and improved method for quenching steel, and particularly high carbon steel, wherein a non-ionic, substantially non-foaming wetting agent such as Sterox CD, a polyoxyethylene ester of tall oil, is utilized in a brine solution for obtaining a uniformly hardened surface on the steel.

Other objects of this invention will become evident from the following description of the invention and from the claims appended hereto.

The method of this invention involves the treatment of steel, and particularly high carbon steel having at least about 0.80% carbon. Generally such steel will have at least about 0.20% manganese also. In any event, with steel articles made of that type of steel having such high carbon content, the prior methods of hardening the surfaces thereof have often resulted in spotty areas of insuflicient hardness which has resulted in the rejection or reprocessing of the steel articles so treated.

In the method of this invention, the steel, or the articles made therefrom, having the high carbon content is initially heated above the upper critical temperature of the particular steel being treated. With a steel having about 0.80% carbon and about 0.20% manganese, it is heated to a temperature in the neighborhood of 1400 F. and 1500 F. When the steel is thus heated above its critical temperature, it is then given a drastic quench. In order to obtain a uniform hardening of the surface of such steel, the quenching medium of this invention is employed in carrying out this method. Such quenching medium is a brine solution, preferably having about 710% NaCl by weight in water to which has been added a non-ionic, substantially non-foaming wetting agent such as a polyoxyethylene ester of tall oil sold by Monsanto Chemical Company under the trademark Sterox CD. As a specific 2,857,301 Patented Oct. 21, 1958 example, the brine solution could have about 9% NaCl by weight in water and the polyoxyethylene ester of tall oil is preferably added in an amount which is above about 0.05% by weight, or more specifically, about 0.1% by weight. From a practical standpoint, the Sterox CD would not be added in amounts above about 0.25% by weight. i

With the use of the above-described quenching medium in carrying out the method of this invention, the surface of the steel is uniformly hardened to a high hardness value in the range of about -65 Rockwell C. None of the areas of insuflicient hardness such as were described above in connection with the prior art are encountered when using the method of this invention. Also, this method requires less time to obtain the same surface hardness of the steel, as compared to the prior known methods.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof and various changes may be made within the scope of the appended claims without departing from the spirit of the invention.

What is claimed is:

l. A method of treating high carbon steel to obtain uniform hardening of the surface thereof, comprising initially heating said steel above its upper critical temperature, and thereafter quenching the heated steel in a brine solution containing a non-ionic, substantially non-forming wetting agent consisting of a polyoxyethylene ester of tall oil.

2. The method set forth in claim 1, wherein said brine solution includes 7-10% by weight of NaCl in water and whereinsaid wetting agent is a polyoxyethylene ester of tall oil which is present in the brine solution in an amount above about 0.5% by weight.

3. The method set forth in claim 1, wherein said brine solution includes 7-10% by weight of NaCl in water and wherein said wetting agent is a polyoxyethylene ester of tall oil which is present in the brine solution in the amount of about 0.1% by weight.

4. A quenching medium for use in the hardening of high carbon steel, comprising a brine solution having therewith an effective amount of a polyoxyethylene ester of tall oil.

5. A quenching medium for use in the hardening of high carbon steel, comprising a brine solution having about 7-10% NaCl and having therewith an amount of a polyoxyethylene ester of tall oil above about 0.05 by weight.

6. A quenching medium for use in the hardening of high carbon steel, comprising a brine solution having about 710% NaCl and having therewith about 0.1% of a polyoxyethylene ester of tall oil.

References Cited in the file of this patent FOREIGN PATENTS 479,069 Canada Dec. 4, 1951 

1. A METHOD OF TREATING HIGH CARBON STEEL TO OBTAIN UNIFORM HARDENING OF THE SURFACE THEREOF, COMPRISING INITIALLY HEATING SAID STEEL ABOVE ITS UPPER CRITICAL TEMPERATURE, AND THEREAFTER QUENCHING THE HEATED STEEL IN A BRINE SOLUTION CONTAINING A NON-IONIC, SUBSTANTIALLY NON-FORMING WETTING AGENT CONSISTING OF A POLYOXYETHYLENE ESTER OF TALL OIL. 